Intelligent reflecting surface (IRS) is an emerging technology to improve the performance of wireless communication systems.
By adaptively adjusting the attenuation and/or phase shift of massive passive reflecting elements, the IRS is able to “program" the wireless propagation channel with low-cost hardware, which shows great potential for improving spectrum efficiency and energy efficiency, especially for millimeter-wave (mmWave) communication system due to its vulnerability to high path-loss and link blockage [1]}, [2]}.
Massive research works on the IRS have been conducted recently, including channel modeling [3]}, [4]}, beamforming design [5]}, [6]}, and hardware experiments [7]}, [8]}.
